1. Field of the Invention
The present invention relates to an image forming device such as a copying machine, a printer, facsimile device, or a composite machine having the functions of all of those machines and device, as well as a transfer device in the image forming device.
2. Description of Related Art
In an electronic copying machine or a printer there is used a transfer device for transferring printing paper as an object to be transferred in a predetermined direction. The transfer device has, as principal components, transferring rolls in various positions of a transfer path which rolls are driven by means of a motor. Heretofore, for stabilizing the state of transfer of printing paper, the printing paper transferring velocity has been made constant by making the number of revolutions of the transferring rolls driving motor constant.
In the conventional transfer device, however, there has been the problem that as the transfer device is used, the paper transferring velocity decreases even if the number of revolutions of the motor is kept constant, due to wear of the transferring rolls or adhesion of paper dust to the transferring rolls. Additionally, due to wear of the transferring rolls or adhesion of paper dust to the same rolls, there arises offset in the transfer of paper, and the occurrence of skew may result. The term “skew” is a generic term for movement or inclined travel of a to-be-transferred object in a direction orthogonal to the transferring direction of the to-be-transferred object.
On the other hand, recently, various machines, especially office machines such as copying machines or printers, are required to be manufactured in high productivity and therefore a delay thereof due to a fault is not allowed, but it is required to promptly detect the fault and remedy it. Particularly, a large number of components capable of operating at high speed and high accuracy are mounted in various recent machines. Above all, drive parts such as motor and solenoid, as well as power transfer parts such as gears and rollers adapted to operate in interlock with the drive parts, including drive circuits for driving motors, etc., are generally high in the frequency of fault occurrence in comparison with other electronic components (passive electronic parts such as resistors and capacitors, or transistors and IC (integrated circuit)). Particularly in the case where the working environment is very bad, even if the components in question are used in a normal manner, there occur various troubles and faults difficult to be detected and a great deal of labor is required for remedying such troubles and faults.
For example, such consumable parts as transferring rolls differ in the degree of wear or deterioration, depending on working conditions and environment conditions of a place where the rolls are installed. Therefore, it is impossible to correctly guess when such consumable parts as transferring rolls are to be replaced. From only the number of transferred sheets of printing paper or from elapsed time, it is impossible to guess when consumable parts are to be replaced. Accordingly, heretofore, such consumable parts have been replaced earlier than an appropriate time, thus giving rise to the problem of a great loss. Thus, measuring a change in paper transferring velocity or a skew quantity and estimating an appropriate time when consumable parts are to be replaced, are essential from the standpoint of executing maintenance and servicing efficiently.
Various mechanisms have been proposed wherein the state of motion of a moving object is detected using a measuring wave. As examples of measuring devices using a measuring wave, there are known optical displacement information measuring devices such as a laser Doppler velocity meter and a laser encoder. The laser Doppler velocity meter measures the moving velocity of a moving object by utilizing the Doppler effect such that when a laser beam is applied to a moving object, the frequency of scattered light from the moving object shifts in proportion to the moving velocity.
Further, there are proposed mechanisms wherein light is applied to an object, then reflected light from the object is received by a photo-detector array, and a structural feature appearing on the surface of the object is observed, thereby detecting the position and motion of the object.
These mechanisms which employ a measuring wave to detect the state of motion of a moving object are considered effective in implementing the function of monitoring movement in transfer direction or in skew direction of printing paper being transferred and controlling the transferring operation on the basis of the result of the monitoring, also effective in implementing a troubleshooting function involving error processing in the event the result of the monitoring should exceed a predetermined reference, and further effective in implementing the function of diagnosing deterioration of transfer-related components.